Such roll stands usually comprise a number of rolls, mostly three rolls, which are each provided on a roll shaft rotatably mounted in the stand housing. In this case, the rolls are arranged relative to one another in such a way that their axes of rotation lie in a plane perpendicularly to the rolling direction at the same distance from a common center point, so that respectively adjacent rolls are at the same angular distance from one another. The rolls thus together form a “roll pass”.
Many configurations of roll stands of this type are known. In order to be able to remove the rolls quickly from the stand and without complicated dismantling work and to be able to exchange them for those with a roll pass recently machined, the roll shafts, in a special embodiment of the roll stands, are each subdivided into two sectional shafts and each roll is clamped in place between two facing end faces of the two sectional shafts in a fixed but releasable manner. The clamping force is applied by means of a tie rod arranged in a central longitudinal bore of the roll shaft and is maintained during the operation of the roll stand.
If a roll is to be changed, only the tie rod is to be released and shifted in the axial direction to such an extent that it clears the separating location of the two sectional shafts. The two sectional shafts are then to be moved apart axially to such an extent that the roll can be removed transversely to the roll shaft.
Rolling-contact bearings normally serve to radially mount the roll shaft in the stand housing, these rolling-contact bearings being arranged on both sides of the roll and thus interacting in each case with one of the two sectional shafts. The rolling-contact bearings in turn are either supported in a corresponding bore directly in the stand housing, or a bearing bush fitted in between the stand-housing bore and the rolling-contact bearings is provided. This bearing bush may be designed as an eccentric bush, so that the roll shaft can be shifted in the radial direction by rotating the eccentric bush relative to the stand housing and thus the distances of the roll-shaft longitudinal axes from the common center point of the roll stand can be set in an infinitely variable manner.
The rolling-contact bearings are normally grease-lubricated, so that an oil-tight seal arrangement, which is costly to produce and is susceptible to faults, between the interior of the bearing device provided in the stand housing and the surroundings can be dispensed with.
However, in order to avoid a situation in which contaminants can reach the rolling-contact bearings through the stand-housing opening, through which the roll emerges with its working periphery, which contaminants would substantially increase the wear of the rolling-contact bearings, it is known to inject air with slight positive pressure in the direction of the stand-housing opening from the ends of the roll shafts, this air, due to the air flow directed outward in the region of the stand-housing opening, essentially preventing ingress of dirt particles.
Since, with increasing volumetric flow, there is the risk of the grease provided for lubricating the bearings being dragged along outward via the stand-housing opening by the air which is flowing through, labyrinth-seal arrangements acting on both sides of the roll between the sectional shafts of the roll axis and the eccentric bush are provided in a roll stand disclosed by the applicant. To this end, the sectional shafts each have a radial straight surface, on which two annular extensions formed concentrically to the roll-shaft axis and extending in the direction of the roll-shaft axis are integrally formed. Complementary annular grooves, in which the extensions engage and thus form the labyrinth-seal arrangement, are accordingly made in a respectively opposite, radial straight surface of the eccentric bush.
As already mentioned, the two sectional shafts can be moved apart in the axial direction by an adjusting displacement for the roll change. To this end, the annular grooves are made in the respective radial straight surface of the eccentric bush to such a depth that there is a distance between the ends of the projections and the base areas of the annular grooves when the roll is fitted, this distance corresponding to at least the adjusting displacement.
Although this configuration reliably produces a sealing effect which reduces the volumetric flow to such an extent that only small quantities of lubricating grease can reach the labyrinth-seal arrangement, the lubricating grease immediately serving here to lubricate the seal arrangement, it is a disadvantage that machining of both the sectional shafts and the eccentric bush is necessary in order to produce this labyrinth-seal arrangement, this machining making the arrangement very costly to produce.